Pneumatic hammer



PATENTED PEB. 2, l1904.

l, 4No. 750,836.

F. K. PASSBTT.

PNBUMATIG HAMMER.

APPLIGATION FILED AUG.20,1902.

2 SHEETS-SHEET 1,

Nov MODEL.

PATENTBD PBBjz, 1904.

F. K. PASSI-ITT.

PNEUMATIC HAMMER.

APPLIOATION FILED AUG.2o,19o2.

2 SHEETS-SHEET 2.

H0 MODEL.

UNITED STATES Patented February 2, 1904.

PATENT OEEICE.

FRANCIS K. FASSETT, OF ST. LOUIS, MISSOURI, ASSIGNOR TO LEO EHRLIOH, OFST. LOUIS, MISSOURI.

PNEUMATIC HAMMER.

SPECIFICATION forming part of Letters Patent No. 750,836, dated February2, 1904.

Application filed August 20, 1902. Serial No. 120,332. (No model.)

T (all wwnt it 72u03/ concern:

Be it known that I, FRANCIS K. FAssE'IT, a citizen of the United States,residing at the city of St. Louis, State of Missouri, have invented acertain new and useful Improvement in Pneumatic Hammers, of which thefollowing is a full, clear, and exact description, such as will venableothers skilled in the art to which it appcrtains to make and use thesame, reference being had to the accompanying drawings, forming part ofthis specification, in whichA Figure l is a longitudinal verticalsectional view throug'h my improved long-stroke pneumatic hammer. Fig. 2is a detail view of the barrel or cylinder partly, in vertical sectionand partly in elevation. Fig. 3 is a sectional view on line 3 3, Fig. l.Fig. 4 is a sectional view on line 4 4, Fig. l. Fig. 5 is a sectionalview on line 5 5, Fig l. Fig. 6 is a sectional view on line 6 6, Fig. l.Fig. 7 is a sectional view on line 7 '7, Fig. l. Fig. 8 is an enlargedfragmentary vertical sectional view showing the parts in normal positionready for operation. Fig. 9 is asimilar view. showing the throttle-valveopen and the valve for the piston slightly advanced from the positionshown in Fig. 8, and Fig. IO is a similar view showing the valve for thepiston in its forward position. A

This invention relates to a new and useful improvement in pneumatichammers of that type known as long-stroke hammers. The tool is designedto be operated by compressed air led to` the tool through a flexiblesupplypipe. In operation the device is held in the hands of an operator,the reciprocations of the piston being utilized to drive rivets, headrivets, calk boilers, &c.

My present invention contemplates a construction wherein the piston ismoved forward by live pressure controlled by a valve preferably locatedin a suitable casing in the rear end of the barrel or cylinder. Upon thepiston reaching its forward position the valve referred to is' bysuitable arrangement of ports shifted, so as to cut off the supply oflive pressure behind the piston and permit the pressure trapped behindthe piston to escape. To facilitate the escape of this trapped pressureand also to return the piston to the rearY end of the barrel orcylinder, I introduce an ejector-nozzle supplied by live pressure andwhich directs the blast into and through the escape-port for the trappedpressure behind the piston, whereby not only is the trapped pressurefacilitated in its escape, but the said ejector-nozzle exhausts the airfrom the space behind the piston to such an extent that the partialvacuum created will cause the piston to move rearwardly. This ejectordevice is only in operation when the piston has reached its forwardposition, the live pressure being cut off therefrom when the piston isrestored to its rear position and in readiness t0 receive live pressure,by which it is again driven forward. It is obvious that by regulatingthe size of the opening in the ejector-nozzle and of the escape-port thelength of time consumed by the piston in its rearward movement may beregulated.

Referring now to the drawings, A indicates the barrel or cylinder, whichis preferably counterbored in its forward end to receive a bushing a.The rear end of the cylinder is also counterbored and receives avalve-block B, containing the main controlling-valve O. The walls of thecylinder at its rear lend are preferably increased in thickness in orderthat a chamber may be formed therein for containing a throttle-valve D.

E indicates a handle-base which is introduced over the enlarged rear endof the cylinder for the purpose of holding the valveblock in positionand also forming one of the end walls of the chamber containing thethrottle-valve. In order that the parts may be sesity for threading thehandle-base on the cyl- IOO button at its outer end and at whose innerend is pivoted an extension g, cooperating with a pin or projection CZon the throttle-valve D. Then plunger G is moved inwardly, thethrottle-valve is moved forwardly against a spring H. It is necessary tohold the throttle-valve in its forward position during the' der ofcorrespondingly-uniform diameter.

The above construction has been illustrated as one of the forms of myinvention; but it is obvious that thesedetails of construction can bechanged in many particulars without departing from the nature andprinciple of my invention, and therefore I do not wish to be understoodas limiting my invention to the particular construction hereinbeforedescribed, except as such limitations may be expressed in the appendedclaims.

I will now describe the port arrangements which lI employ for effectingthe reciprocation of the piston and its controlling-valve.

In the position of the parts shown in Figs. 1 and 8 the throttle-valveis closed. This throttle-valve is preferably cylindrical and providedwith two reduced annuli, forming, substantially, three connected heads.7e will assume that a pipe is connected to the nipple F, through whichcompressed air is supplied to the device. This air entering through thenipple passes through a groove l, preferably formed in the barrel,whence it is ported to the valve-chamber containing the throttlevalve.Then the throttle-valve is closed, the port from the chamber 1 registerswith the space between the middle and forward heads; but when thethrottle-valve is moved forward, as shown in Figs. 9 and 10, the portfrom chamber l communicates with thespace between the middle and rearheads of the throttle-valve, which space establishes communicationbetween live-pressure chamber l and a passage 2, formed inthevalve-block. The main control- 'ling-valve C is formed hollow, and itschamber in the valve-block is of varying diameters, to which theexternal diameters of the several portions of this valve correspond. Tewill assume for the present that the valve C is in its rearmostposition, in which openings 3, registering with the chamber 2, willadmit pressure into the interior of the valve, and said pressure findingno point of escape through the rear end of the valve will at the forwardend of said valve pass into a circular groove 4 in the valveblock andthence forwardly through suitable openings 5 intothe space behind thepiston.'

(See Fig. 6.) i Under these conditions the pis-` ton will be movedforwardly in the cylinder until its rear end uncloses a port 6 in thecylinder just before the piston delivers its impacting blow. Theposition of the piston in delivering its impacting blow is indicated bydotted lines and z/ in Fig. 1. Port 6 opens into a passage 7, formed inthe cylinder, which passage communicates at its rear end with an annulargroove or chamber 8 in the valveblock, which encircles the chamber, inwhich operates a large centrally-located head of the valve. This head,as clearly shown in Figs. 8, 9, and 10, is formed with an annular groove9, designed when the valve is in its rearmost position to register withthe groove 8, and from which groove 9 lead openings 10 to the rear faceof the enlarged head of the valve. Thus when port 6 is opened to livepressure when the piston reaches the forward limit of its movement saidlive pressure is admitted behind the enlarged centrally-located head ofthe Y main valve, tending to move said valve forwardly, so as to closethe ports which admit pressure behind the piston. As the piston mayafter delivering its blow rebound or/start back upon its returnmovement, closing port 6 and other ports depending upon it for livepressure to hold the valve forward, I do not rely upon this port 6 forthe constant admission of live air behind the enlarged head of thevalve. On the contrary, the grooves 8 and 9, as shown, are narrow, andafter the first impulse of air through port 6 said grooves pass out ofregistration, and even though the piston remains forward, so as to leavethe port 6 unclosed, this source of supply would be shut off by thisaction. (See Fig. 9, wherein the valve is starting on its forwardmovement.) In view of these conditions I arrange a port 11, leading fromthe live chamber 2 to the enlarged bore of the valve-chamber, which port11 when the valve moves forward so as to place grooves 8 and 9 out ofregistration is open, and live pressure is now directly admitted behindthe enlarged head of the valve to insure a continuation of its forwardmove- IOO IIO

ment to the full limit and also to hold said valve in its forwardposition.

12 indicates a port much larger than port 11, which leads from the spacebehind the enlarged head of the valve into a passage 13, formed in thecylinder and terminating in a port 14 in the cylinder slightly inadvance ofi Y I tioned conditions blows through port 14, and while thevalve is held in its forward position it is at the same time sensible topressure in front of its enlarged head, which pressure is relied upon tomove the valve rearwardly. The pressure for moving the valve rearwardlyis obtained from the space behind the piston through ports 15, (see Fig.6,) which are drilled through the valve-block, preferably alongside ofbut not communicating with ports 5. These ports at all times maintaincommunication with the space in front of the enlarged head of the valveand the space behind the piston. As means now about to be described' areprovided for cushioning the piston on its rear movement, said cushionbeing in the nature of trapped dead air, the cushioning-air passesthrough ports to the space in front of the enlarged head of the valveand forces the valve rearwardly, so as to shut o the admission of livepressure through port 11 to the space behind said enlarged head and alsoto place grooves 8 and 9 into registration for another operation. Port 6when the piston is in its rearmost position is open to atmosphere, andof course no pressure will pass therethrough tending to move the valveforwardly.

As shown in Fig. 8, when the valve is in its rear position to admitpressure behind the piston openings 3 register with the live-air chamber2 and the forward end of the valve is behind the groove 4, so that saidgroove is open to permit live pressure to pass into the space behind thepiston. About the time that the piston approaches the limit of itsforward movement the valve is thrown to its forward position, as abovedescribed, in which event the openings 3 are moved out of registrationwith the live-pressure chamber 2 and the forward end of the valve closesthe groove 4. The valve is in this forward position during the initialoperation of the return or rearward movement of the piston and untilsuch time as the cushioning pressure above described is produced, whichis at or about the time the piston is in its rearmost position.

I will now describe the general exhaust for the pressure heretoforereferred to as being trapped behind the piston.

By referring to Fig. 10, it will be noted that the valve-block at itsforward end does not entirely iill the counterbore in the rear end ofthe cylinder, and thus an annulus 16 is formed. The periphery of theforward end of the valveblock is provided with longitudinally-disposedgrooves 17, (see also Fig. 7 which communicate with the groove 16 andwith a groove 18. Openings 19 (see Fig. 6) extend inwardly from groove18 in front of the forward edge of valve C. Valve C never closes theseopenings 19. rlhe rear end of the valve cooperates with an annulargroove 20, which, as shown in Figs. 3 and 10, communicates with anexhaust-space v21. 22 represents openings formed through the handle-baseand the rear end of the cylinder, said openings communicating with theexhaust-space 21 and the cylinder portion of said openings beingthreaded, so as to receive plugs 23. These plugs form additional meansof securing the handle-base to the cylinder, as I preferably make themof such length that they extend outwardly into the openings in thehandle-base. to is provided with a contracted opening 24, through whichthe exhaust passes. While I have shown two of these exhaust-plugs in thedrawings, it is obvious that one of such plugs may be employed, or morethan two of such plugs may be employed, if desired.

When the valve is in its forward position, it is obvious that pressurebehind the piston will find a ready means of escape through the exhaustopenings and passages hereinbefore referred to, and this action wouldundoubtedly result in a natural way. I have provided means, however, forfacilitating this exhaust and also for creating a partial vacuum behindthe piston for restoring the same in readiness for another stroke. Thismeans consists of an ejector nozzle or nozzles, preferably screwed intoposition and in axial alinement with the exhaust plug or plugs 23. (SeeFigs. 4 and 10.) The contracted nozzle-openings in these ejector-plugs25 communicate with an annular groove 26, which groove when the valve isin its forward position by means of a reduced portion 27 in said valveis in direct communication with the live-pressure chamber 2. By thismeans when the piston reaches the forward extremity of its movement, asbefore described, the valve C will be moved forward to open theexhaust-passages for the escape of pressure behind the piston, andsimultaneously live pressure will be admitted to the ejector-nozzles,which results not only in facilitating the escape of the exhaust, but inthe creation of a partial vacuum behind the piston, which causes saidpiston to move rearwardly or be set in position for another operation.The speed of this rearward movement of the piston is preferably suchthat at or near its extremity the rear end of the piston will close thegroove 16, thus shutting off the means of exhaust of pressure frombehind the piston, and the momentum gathered by the piston in itsrearward movement is such that the air trapped in the forward end of thevalve-block (at a point behind the groove 16) will be compressed. Thistrapped air in the forward end of the valve-block not only provides acushion for the piston on its rearward stroke, but also provides a meansfor operating' the valve C, (through openings 15,) moving said valverearwardly in position to again admit pressure behind the piston.

Upon throwing the throttle-valve when the valve C is in position toadmit pressure behind the piston it is obvious that the engine willstart irrespective of the position of the piston. If, however, the valveC were in a Each of the plugs referred lOO IIS

forward position, as shown in Fig. 10, it is obvious that the only workbeing done by the pressure is in connection with the ejector device, andif the piston should occupy a position so close to the groove 16 'or belocated within the pocket in the front end of the valve-block, so thatno momentum could be built up to form a cushion to actuate the valve Cand move it rearwardly, the engine would not start and its point wouldhave to-be depressed, so as to permit gravity to act on the valve andpiston, moving' them forwardly, resulting in loss of time. To obviatethis diiiiculty, I provide ashoulder 28 on the valve, which shoulder isdesigned whenthe throttlevalve is moved forward from its home positionto receive pressure for a short period of time and throw the valverearwardly. By referring to Fig. 8 it will bel observed that the spacebetween the middle and forward heads of thethrottle-valve is such thatsaid valve in its forward movement will temporarily establishcommunication between the pressure-port 1 and a port 29, which leads toan annular groove 30 in front of the head or shoulder 28. In its forwardmovement the throttle-valve will admit pressure in front of the shoulder28 and until the middle head of the throttle-valve has closed the livepassage 1. A continued forward movement of the throttle-valve will opensaid live passage 1 and establish communication therebetween and thelive chamber 2 and close port 29 against live pressure. Port 29,however, while closed to pressure is in this forward position of thethrottle-valve opened to atmosphere via port 31, opening into thechamber containing the throttle-valve-operating plunger. Thusdisplacement ofair in front of shoulder 28 is taken care of.

It will be noticed that the rear face of the enlarged head of the valveChas a larger area than the front face of said enlarged head. This ismade necessary from the fact that when the valve is in its rearmostposition, as shown in Fig. 8, and pressure is admitted to the spacebehind the piston said pressure will also act against the reduced frontface of the valve-head through the ports 15. When port 6 is open andlive pressure is admitted behind the head, the rear face having thegreater area, said pressure admitted through port 6 will preponderateand move the valve forwardly until the port 11 is open, which, as beforedescribed, will cause the valve to continue its forward movementnotwithstanding the presence of pressure in front of the enlarged head.

In order to get the valve C, with its enlarged centrally-located head,in the valveblock, I preferably form said valve-block in two parts, theline of separation being at the forward end of the chamber containingthe enlarged head.

' piston strikes the shank of the tool.

forward end of the piston strikes the shank of the tool or chisel. Theseopenings 32 serve for the displacement of air due to the movement of thepiston in the cylinder. It will thus be seen that there is nothing infront of the piston to retard its movement until the I rely upon nopressure in front of the piston to restore the same, as will be evidentfrom the foregoing description, and consequently there is no forwardwall or cylinder-head with appropriate port arrangements to admit andexhaust pressure therebetween and the forward face of the piston todrive the` piston rearwardly. Furthermore, as the shank of the tool isnot relied upon in my construction to form the front wall of thecylinder to hold pressure in the cylinder, as is done in some cases, itis obvious that the tool may be fitted loose in the front end of mycylinder and be perfectly free to move, so as to receive and transmitthe full force of the impacting blows of the piston. In suchconstructions referred to where the shank of the tool is fitted snuglyin the forward end of the barrel to make an air-tight joint and serve asan end wall for the cylinder it is obvious that when the piston movesforwardly the air in advance thereof is compressed to an extent that thefull force of its blow is not delivered upon the shank of the tool. Onthe contrary, the cushion in front of the piston materially decreasesthe force of the blow of the piston. IV hen the piston is about todeliver its blow, in some constructions, the pressure is admitted infront thereof to lift the piston when it rebounds from its blow. Theadmission of this pressure is controlled by a valve actuated by thecushion, and the pressure of this cushioning-air must be sufiicient tothrow said valve, and to this extent the effectiveness of the blow ofthe piston is decreased.

So far asI am aware I am the first to a1'- range displacement-openingsin front of the piston of a long-stroke hammer which will accommodatethe movement of the piston,but do not contribute in any way to returningsaid piston rearwardly. means acting only on the rear face of the pistonfor actuating said piston.

I am aware that many minor changes in the construction, arrangement, andcombination of the several parts of my device can be made andsubstituted for those herein shown and described without in the leastdeparting from the nature and principle of my invention.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, isy l 1. Apneumatic hammer comprising a cylinder, apiston, a handle-base, and a nipple-plug introduced through an openingin the handlebase and into the cylinder for locking the parts 4together; substantially as described.

Q. A pneumatic hammer comprising a cylin- IOO IIO

I am also the first to provide der, a piston, al handle-base, avalve-block held in position by the handle-base, and a nippleplug forsecuring' the handle-base in position on the cylinder; substantially asdescribed.

3. A pneumatichammer comprising a cylinder, a piston, a handle-base, anda threaded plug' for the attachment of a supply-pipe, said plug' lockingsaid handle-base in position on the cylinder; substantially asdescribed.

4. A pneumatic hammer comprising a cylinder, a piston, a handle-base,and a plug passing through an opening in the handle-base and threadedinto the cylinder, said plug being formed with an opening' for theexhaust; substantially as described.

5. In a pneumatic hammer, the combination with a cylinder having acounterbore in its rear end, of a valve-block arranged in saidcounterbore and provided with a pocket in its inner end to receive andcushion the rear end of the piston, and means for holding saidvalve-block in position; substantially as described. A

6. In a pneumatic hammer, the combination with a cylinder, of a pistonof uniform diameter throughout its length, said cylinder having acounterbore in its rear end, and avalve-block arranged in saidcounterbore and provided with a pocket in its inner end having adiameter corresponding to the bore of the cylinder, whereby the pistonis received in said pocket and cushioned; substantially as described.

7. In a pneumatic hammer, the combination with a cylinder and itspiston, of ahollow valve for admitting' pressure behind the piston, saidvalve being provided with an enlarged head, a groove 8 in the chambercontaining said enlarged head, a passage 7 leading from said groove andterminatingin a port 6 in the cylinder, which port is controlled by thepiston, a groove 9 in the enlarged head of the valve, from which groovelead openings l to one side of said enlarged head, whereby, when port 6is open to pressure, the valve is initially moved to shut o theadmission of pressure behind the piston, such movement continuing whilegrooves 8 and 9 remain in registration, and a port 11 for admittingpressure to effect a continued movement of said valve, said port beingopened by the valve when the grooves 8 and 9 pass out of registration;substantially as described.

8. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting pressure behind the piston, a portcontrolled by the piston for effecting an initial movement of saidvalve, a port controlled by the valve for admitting pressure to effect acontinued movement thereof, and an escapeport controlled by the piston,whereby the pressure which actuates the valve is permitted to blowthrough to relieve the valve; substantially as described.

9. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting pressure behind the piston, said valvehaving an enlarged head, a port under control of the piston foradmitting an impulse of pressure behind the enlarged head to move thevalve, said valve in such initial movement opening a port for admittinglive pressure behind said head, anda passage leading from the chamberbehind the enlarged head of the valve to a port in the cylinder locatedin advance of the first-mentioned port, whereby, when the piston is in aforward position, the first-mentioned port is opened and thelast-mentioned port closed, said last-mentioned port being opened by thepiston when said piston is in position on its rearward stroke to relievethe pressure behind the enlarged head of the valve and rendery the samesensitive to action under opposing pressure; substantially as described.

10. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting and exhausting pressure to and from thespace behind the piston, means controlled by said piston for effectingthe movement of said valve in one direction to close the ports whichadmit pressure behind the piston, means controlled the piston forrelieving the valve of pressure which holds it in its closed position,and ports for conducting air under pressure developed by the momentum ofthe piston on its rearward movement for throwing the valve in theopposite direction to open the admission-portsgsubstantially asdescribed.

11. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valveblock having a live-pressure chamber and an exhaustchamber, and a hollow valve arranged in said block for controlling portsleading to said chambers, said valve-block having a pocket formed in itsforward end to receive the rear end of the piston; substantially asdescribed.

12. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valveblock having a pressure-chamber 2, and a hollow valvehaving ports 3 designed in certain positions of the valve to registerwith such pressure-chamber, said valve-block also having an annulargroove 4 and openings 5, communication between the interior of thecylinder and said groove being controlled by the position of said valve;substantially as described.

13. In a pneumatic hammer, the combination with a cylinder and itspiston, 0f a valveblock having an exhaust chamber formed therein, ahollow valve through which the exhaust passes, a space in said valvecommunieating with the exhaust-chamber in certain positions of thevalve, said valve-block having passages 17 and 18 communicating with thecylinder and at all times in communication with the space inside of thehollow valve; substantially as described.

IOO

IIO

14. In a pneumatic hammer, the combination with a source of constantair-supply, acylinder and its piston, means for admitting pressurebehind the piston to drive the same forward ly, and means for exhaustingthe pressure behind the piston to draw the piston rearwardly;substantially as described.

15. In a pneumatic hammer, the combination with a source of constantair-supply, a cylinder and its piston, means for admitting pressurebehind the piston to drive the same forwardly', and means for creating apartial vacuum behind the piston for drawing the same rearwardly;substantially as described.

16. In a pneumatic hammer, the combination with a source of constantair-supply, a cylinder and its piston, a valve for intermittentlyadmitting pressure behind the piston, and means controlled by said valvefor creating a partial vacuum behind the piston; substantially asdescribed.

17. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve operated by the piston, said valve in one positionadmitting pressure behind the piston, and means controlled by the valvein its other position for creating a partial vacuum behind the piston;substantiallyY as described.

18. In a pneumatic hammer, the combination with a cylinder and itspiston, of means for admitting' pressure behind the piston to drive thesame forwardly, and an ejector which is operative wheh the pistonreaches its forward limit for creating a partial vacuum in the spacebehind the piston; substantially as described.

19. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting' pressure behind the piston, anejector-nozzle, and a port controlled by said valve for admittingpressure to said ejectornozzle, whereby, when the valve is operated tocut off all pressure behind the piston, the blast issuing from saidejector-nozzle becomes effective to create a partial vacuum to move thepiston in an opposite direction; substantially as described.

20. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting pressure behind the piston, meanscontrolled by said piston for eifecting a movement of said valve, and aplurality of ejector-nozzles to which pressure is admitted by the valvewhen said valve is moved to a position to cut off the admission ofpressure behind the piston, whereby said nozzles act to create a partialvacuum behind the piston to restore the piston; substantially asdescribed.

21. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting pressure behind the piston, a shoulderon said valve, a port for admitting pressure against said shoulder, anda throttlevalve for establishing communication between said port andlive pressure upon its initial movement from its home or closedposition, said throttle-valve in its open position closing said port;substantially as described.

22. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting pressure behind the piston, athrottle-valve, a port controlled by said throttle-valve for moving thefirst-mentioned valve into operative position, and means controlled bythe throttle-valve for establishing communication between said port andatmosphere after said valve has been actuated; substantially asdescribed.

23. In a pneumatic hammer, the combination with a cylinder and itspiston, of a valve for admitting pressure behind said piston, a shoulderon. said valve, a port for admitting pressure against said shoulder, anda throttlevalve for temporarily admitting pressure through said port andagainst said shoulder, said throttle-valve, by a continued movement,

opening said port to atmosphere, so as to ac' commodate displacement ofair resulting from a subsequent operation of the valve; substantially asdescribed.

24. In a long-stroke pneumatic hammer, the combination with a cylinder,of a piston whose stroke exceeds its length, means for admittingpressure only to the rear face of the piston for forcing the pistonforwardly, and means for creating the partial vacuum behind the pistononly for causing the piston to move rearwardly; substantiallyasdescribed.

25. In a long-stroke pneumatic hammer, the combination with a cylinder,of a piston wholl y contained in the cylinder and whose stroke eX- ceedsits length, openings in the front end of the cylinder for accommodatingthe displacement of air resulting from the movement of thefpis'ton, andmeans acting on the rear face only of the piston for operating thepiston; substantially as described.

26. In along-stroke pneumatic hammer, the combination with a cylinder,of a piston wholly contained therein and whose stroke exceeds itslength, said cylinder being provided with openings to atmosphere aboutthe point where the piston delivers its impacting-blow upon the shank ofthe tool, a valve for admitting pressure to drive the piston forwardly,and means controlled by said valve for creating a partial vacuum behindthe piston to retract the same; substantially as described.

In testimony whereof I hereunto a-iix my signature, in the presence oftwo witnesses, this 15th day of August, 1902.

FRANCIS K. FASSETT.

IVitnesses:

GEORGE BAKEWELL, G. A. PENNINGTON.

IOO

